The present invention relates to a method for the formation of a silicon oxide film on the surface of a substrate. More specifically, the present invention relates to a method for the formation of a thick silicon oxide film which is free of cracks and pinholes and which is insoluble in organic solvents.
The formation of a protective film on the surface of a substrate is a technique in general use. In the particular case of the electric/electronic industries, there has been a very substantial increase in the complexity of semiconductor devices and in topographical variations on the surface of semiconductor devices in association with recent increases in the degree of integration and layer count. An interlevel dielectric layer may be formed on the surface of a semiconductor device in order to planarize the topographical variations on the surface of the device, while a passivation coating can be laid down on the surface of a semiconductor device in order to protect it from mechanical damage, chemical damage, damage due to static, ionic contaminants, nonionic contaminants, radiation damage, and so forth.
Silicon oxide films are typically used for the interlevel dielectric layers and passivation coatings formed on semiconductor device surfaces. Chemical-vapor deposition (CVD) and spin-coating are examples of the methods used to form these silicon oxide films. As examples of methods for the formation of silicon oxide film on a semiconductor device surface by spin-coating, Japanese Patent Application Laid Open [Kokai or Unexamined] Numbers Sho 60-124943 [124,943/1985] and Sho 63-144525 [144,525/1988] and U.S. Pat. No. 5,145,723 propose the formation of a film of hydrogen silsesquioxane resin on the surface of the substrate (e.g., the semiconductor device, etc.) and subsequently heating the resin film-bearing substrate in air in order to form a silicon oxide film.
However, the methods proposed in Japanese Patent Application Laid Open Numbers Sho 60-124943 and Sho 63-144525 and U.S. Pat. No. 5,145,723 for silicon oxide film formation are not able to produce a silicon oxide film thicker than 0.6 micrometers (6,000 angstroms). As a result, these methods cannot completely planarize the topographical variations encountered on the surfaces of semiconductor devices, i.e., topographical variations or height differences in excess of 1.0 micrometers (10,000 angstroms). In addition, when the production of a thick silicon oxide film is attempted by these methods, cracks and pinholes are produced in the silicon oxide film and the reliability of the semiconductor device is drastically reduced.
The inventors conducted extensive research into the cause of the inability of the methods proposed in Japanese Patent Application Laid Open Numbers Sho 60-124943 and Sho 63-144525 and U.S. Pat. No. 5,145,723 to produce thick silicon oxide films. As a result, in the case of methods in which the substrate is heated from the very first in an oxygen-rich atmosphere after formation of the hydrogen silsesquioxane resin film on the substrate, it was discovered that crosslinking in the resin develops rapidly and large internal stresses appear in the resin film, which results in the production of cracks. It was also discovered that crack-free silicon oxide films with maximum thicknesses in excess of 1 micrometer can be produced through the reduction in crosslinking rate and relaxation in internal stresses in the resin film that are afforded by a method in which the substrate carrying the hydrogen silsesquioxane resin film is initially heated in an inert gas atmosphere in order to convert the hydrogen silsesquioxane resin film into a preceramic silicon oxide and is subsequently heated in an oxygen atmosphere or mixed gas atmosphere of oxygen plus inert gas. Said preceramic silicon oxide refers to a material which is a precursor for ceramic silicon oxide and which is already insoluble in organic solvent although its crosslinking is not as advanced as in ceramic silicon oxide.
The present invention takes as its object the introduction of a method for the formation of an organic solvent-insoluble, crack-free and pinhole-free silicon oxide thick film.